AT&T's effort to color Google a hypocrite on Net neutrality has won some supporters on Capitol Hill, with a bipartisan group of 20 members of the House attaching their names to a letter calling on the Federal Communications Commission to open an investigation into Google's voice application.

The lawmakers, who represent largely rural districts, asked FCC Chairman Julius Genachowski to open the probe in response to Google's policy of restricting calls in certain rural areas on its Google Voice mobile application.

Google (NASDAQ: GOOG) has explained that the restrictions stem from the steep rates some local carriers charge long-distance providers to route calls in their coverage areas, and justified its policy under the law because it is not a regulated phone company.

Under the common carrier laws that govern phone companies, long-distance providers such as AT&T (NYSE: T) are obligated to connect the calls. AT&T has complained that local providers charge excessive rates for the connections, and that they partner with services like conference call centers and adult chat lines to funnel more traffic to their networks, further gouging the larger phone companies.

In a letter to the FCC last month, AT&T complained that Google blocking phone calls through its voice app set up a double standard, giving the search giant license to dodge the hefty connection fees that AT&T and other phone companies are required to pay.

The lawmakers seem to take AT&T's part in the matter.

"It is our opinion a company should not be able to evade compliance with important principles of access and competition set forth by the FCC by simply self-declaring it is not subject to them without further investigation," they wrote. "If Google is allowed to operate its telephone services outside of the rules by which all other common carriers operate, we worry that the market and support for universal service will be undermined."

In a blog post explaining Google's position, Rick Whitt, the company's telecom counsel, said that Google favored reforms to the carrier-compensation system. At the same time, Google Voice is a Web-based software application, Whitt said, arguing that it is outside the scope of common carrier laws.

For Robert Quinn, AT&T's senior vice president of federal regulatory affairs, that distinction doesn't hold water. In his letter to the FCC chairman, Quinn said that "Google Voice appears to be nothing more than a creatively packaged assortment of services that are already quite familiar to the commission."

Further, Quinn framed the issue in the context of the Net neutrality debate that has vaulted onto the FCC's agenda. He argued that Google is talking out of both sides of its mouth when it supports rules to prevent ISPs from blocking Web traffic while at the same time restricting consumers in certain areas from making calls through its Web-based voice service.

Whitt had an answer for that, too.

"AT&T is trying to make this about Google's support for an open Internet, but the comparison just doesn't fly," he said. "The FCC's open Internet principles apply only to the behavior of broadband carriers -- not the creators of Web-based software applications."

The FCC has already been looking into Google Voice through an inquiry centered around the decision not to accept the service from Apple's iPhone app store. Apple (NASDAQ: AAPL) said that it blocked the app because it altered the iPhone's user interface, but told the FCC that it was reviewing the decision, holding out the possibility that it would eventually admit Google Voice into its app store.

FCC examines 'middle mile' market

Separately, the FCC has opened an inquiry into another nettlesome issue concerning intercarrier compensation. On Thursday, the agency called for comments on the state of the "middle mile" market, where smaller carriers pay their larger rivals for access to their voice and data networks.

That fight has pitted firms like T-Mobile and Sprint against the Bells, with the smaller firms arguing that they are getting gouged for so-called "special access" pricing.

Earlier this year, an array of small carriers, tech firms and advocacy groups launched the "No Choke Points" coalition as a united front to prevail on the FCC to enact tougher regulations overseeing the special access market, where reliable data about pricing has been notoriously difficult to come by.